Production of an α-olefin oligomer using, as the raw material, an α-olefin such as ethylene is performed while cooling the reaction system, because the oligomerization reaction is an exothermic reaction. Therefore, various studies have been made on the industrial method for continuously producing an α-olefin oligomer while removing the heat of reaction generated in the reactor.
For example, Patent Documents 1 and 2 describe a method for producing an α-olefin oligomer having an average molecular weight of 50 to 350 by oligomerizing ethylene in the presence of a catalyst, where part of gas of the gas phase inside a reactor is cooled and condensed in a heat exchanger not in direct contact with a liquid phase by using the gas of the gas phase inside the reactor as a coolant and the heat of polymerization is removed using the condensed liquid, thereby preventing fouling of the heat exchanger.
Patent Document 3 describes a production method of an α-olefin oligomer, including introducing gas in a reactor into a heat exchanger, and circulating the gas and condensate liquid obtained from the outlet of the heat exchanger to the reactor, where the gas linear velocity of the gas phase inside the reactor is controlled to fall in a predetermined range so as to prevent a reaction solution from entrainment in the gas phase.
Patent Document 4 describes a method of cooling the top of a reactor by the use of a cooling agent such as propylene when producing an α-olefin oligomer such as 1-hexene by oligomerizing ethylene in the presence of an organic solvent and a homogenous catalyst in a reactor, where the reactor top temperature is controlled to be from about 15° C. to about 20° C. by utilizing a condenser to enhance an internal cooling cycle.
Patent Document 5 describes a technique of feeding a liquefied hydrocarbon (α-olefin) from the bottom of the reactor liquid phase at the time of oligomerization of a hydrocarbon, and Patent Document 6 describes a technique of feeding a liquefied hydrocarbon and a liquefied evaporative coolant from the bottom of the reactor liquid phase.